CVE-2025-20718 is a stack overflow vulnerability classified under CWE-121, found in the wlan AP driver of several MediaTek chipsets including MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986. The root cause is an incorrect bounds check that allows an out-of-bounds write on the stack, which can be exploited by a local user with execution privileges to escalate their privileges on the device. The vulnerability does not require user interaction, making it easier to exploit once local access is obtained. Affected software versions include MediaTek SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02, which are commonly used in embedded wireless devices and routers. The vulnerability impacts confidentiality, integrity, and availability by potentially allowing attackers to execute arbitrary code with elevated privileges, manipulate sensitive data, or cause denial of service. Although no public exploits have been reported yet, the high CVSS score of 7.8 reflects the significant risk posed by this flaw. The issue was assigned by MediaTek and published in October 2025, with patch identifiers indicating that fixes are planned or available. The vulnerability is particularly relevant for devices deployed in enterprise and critical infrastructure environments that rely on MediaTek wireless chipsets for network connectivity.

For European organizations, this vulnerability poses a significant risk to network infrastructure devices such as wireless access points and routers that incorporate the affected MediaTek chipsets. Successful exploitation could lead to local privilege escalation, enabling attackers to gain control over network devices, intercept or manipulate network traffic, and disrupt network availability. This could compromise sensitive data confidentiality and integrity, especially in sectors like finance, healthcare, and government where secure wireless communication is critical. Additionally, compromised devices could be used as footholds for lateral movement within corporate networks or as part of botnets for broader attacks. The impact is heightened in environments where devices run outdated SDKs or openWRT versions, which are common in embedded systems across Europe. The lack of required user interaction lowers the barrier for exploitation once local access is obtained, increasing the threat to organizations with multiple users or less restrictive local access controls.

1. Apply vendor-provided patches or firmware updates as soon as they become available to address the vulnerability in the affected MediaTek chipsets and software versions. 2. For devices running openWRT 19.07 or 21.02, upgrade to versions that include the security fix or apply backported patches. 3. Restrict local user access to devices with affected chipsets by enforcing strict access controls and limiting administrative privileges. 4. Monitor device logs and network traffic for unusual activity indicative of exploitation attempts, such as unexpected wlan driver errors or privilege escalations. 5. Implement network segmentation to isolate critical wireless infrastructure from general user networks, reducing the risk of local exploitation spreading laterally. 6. Conduct regular security audits of embedded devices and wireless infrastructure to ensure firmware is up to date and configurations follow best security practices. 7. Educate IT staff about the vulnerability and the importance of timely patching and monitoring to reduce the window of exposure.